Marker mechanism

ABSTRACT

A gas powered marker comprises a stepped bolt which is projected forward during firing by compressed gas in a chamber acting on a rearward facing surface of the bolt and which is projected backwards by compressed gas in a chamber acting on a forward facing surface of the bolt. In the rearmost position the force acting on the forward facing surface is greater than the force on rearward facing surface and firing of the marker is achieved by venting to atmosphere the compressed gas acting on the rearward facing surface.

FIELD OF THE INVENTION

This invention relates to an improved mechanism for a gas operated marker, i.e., a marker which fires a (paint-filled) projectile by means of compressed gas. Markers of this kind can be used in forestry for marking trees and are also used in paintball games in which balls of paint are fired at other players to mark them.

DESCRIPTION OF THE PRIOR ART

Many conventional markers have a hollow bolt which, when the trigger is pulled to fire the marker, is driven by compressed gas from a rearward position to a forward position in the breech. As the bolt moves forward it pushes forward a paintball which has been loaded into the breech—usually by gravity from a magazine located above the breech. In the forward position of the bolt bores opening to its interior are exposed to compressed gas in a cylinder surrounding the bolt, causing the paintball and the compressed gas to be expelled from the marker. After this the bolt is moved back to its rear position, in which the bores are isolated from the cylinder and the flow of compressed gas from the cylinder to the breech is stopped. A disadvantage of this otherwise simple arrangement is that more compressed gas is used than is actually necessary to fire the paintball from the barrel. This means that the source of compressed gas—a compressed air storage cylinder connected to the marker housing—has to be refilled frequently, which is both expensive and inconvenient.

U.S. Pat. No. 5,613,493 seeks to address this problem by attaching a spool valve to the rear of the bolt. A fill chamber and a dump chamber are positioned in the marker housing behind the bolt. In the rear position of the bolt both chambers are filled with compressed gas, but when the bolt moves forward the spool valve isolates the chambers so that only the gas stored in the dump chamber escapes through the hollow bolt to fire the selected paint ball. A drawback of this marker is its complexity, the additional length of the marker required to house the spool valve, the weight and inertia of the spool valve and relatively high manufacturing and maintenance costs.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an efficient, compact marker.

In accordance with the present invention there is provided a mechanism for a gas operated marker having a housing and a trigger, the mechanism comprising a hollow bolt slideably mounted on a bolt guide fixed relative to the marker housing, the bolt being adapted to move to a forward position on the bolt guide when the trigger of the marker is pulled to fire a paint ball and then to return to a rear position on the bolt guide after the ball has been expelled from the barrel. The bolt has a first circumferential face which is exposable to gas at a first pressure which produces a rearward force on the bolt and a second circumferential face which is exposable to gas at a second pressure which produces a forward force on the bolt.

In a preferred embodiment of the present invention the gas at the first pressure can be provided in an annular chamber surrounding the bolt and at least some of the gas at the second pressure can be stored in a cylindrical chamber occupying the interior of the bolt guide. The cylindrical chamber can communicate with the second circumferential face on the bolt via at least one longitudinally extending port formed in the bolt guide wall. Sealing means such as, not limited to, O-rings in circumferential slots formed in the bolt and bolt guide are arranged to isolate the cylindrical chamber from the interior of the barrel of the marker when the bolt is in the rear position. The projected area of the first face in the longitudinal direction of the bolt and the first pressure, and the projected area of the second face in the longitudinal direction of the bolt and the second pressure are chosen so that when the annular chamber is charged with gas at the first pressure and the cylindrical chamber is charged with gas at the second pressure then the rearward force on the bolt is greater than the forward force on the bolt. This holds the bolt in the rear position. Forward movement of the bolt during firing is achieved by reducing the first pressure, preferably by venting the annular chamber though a multipath valve to ambient pressure. As first pressure drops the rearward force on the bolt falls below the forward force on the bolt and the bolt is driven forward. This forward motion (also called “advancement”) of the bolt opens up a passageway between the cylindrical chamber, the at least one longitudinally extending port, the interior of the bolt and the interior of the barrel, allowing the compresses gas in the cylindrical chamber to vent out through the barrel. Rearward movement (also called “retraction”) of the bolt after firing is preferably achieved by operating a valve, preferably a multipath valve, to re-establish the first pressure in the annular chamber.

During rearward movement of the bolt a supply of gas at the first pressure is connected via a filling valve to a second annular chamber which is in communication with the cylindrical chamber via the at least one port in order to refill the cylindrical chamber with compressed gas. The supply of gas at the first pressure is connected by a valve, preferably, if used, the multipath valve for re-establishing the first pressure in the annular chamber, to the first annular chamber where it acts on the first circumferential face on the bolt, causing the bolt to move backwards.

Several figures are provided to aid in the understanding of the present invention. Corresponding elements in the different have been given the same reference numerals. The scope of the present invention is neither limited to these figures nor to the examples of embodiments described below.

DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will now be described by way of non-limitative example with reference to the accompanying drawings, in which:

FIG. 1 shows an example of an embodiment of a marker in accordance with the present invention;

FIG. 2 a illustrates schematically in section part of the mechanism of the marker of FIG. 1 showing the bolt in its rearward position;

FIG. 2 b illustrates schematically in section part of the mechanism of the marker of FIG. 1 showing the bolt in its forward position;

FIGS. 3 a-3 e show schematically exploded views in section of three embodiments of bolts, enlarged views of portions thereof, and other marker components, in accordance with the present invention;

FIGS. 4 a and 4 b show enlarged views corresponding to FIGS. 2 a and 2 b of the first embodiment of a bolt in accordance with the present invention;

FIG. 5 a shows schematically a section through a second embodiment of a bolt in accordance with the present invention in the forward position;

FIG. 5 b shows a partial enlargement of the bolt of FIG. 5 a;

FIG. 6 a shows schematically a section through a third embodiment of a bolt in accordance with the present invention in the forward position;

FIG. 6 b shows a partial enlargement of the bolt of FIG. 6 a.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1, 2 a, 2 b, 3 a, 4 a and 4 b show schematically an example of a marker 1 provided with a first embodiment of a bolt in accordance with the present invention. Marker 1 has a hollow, tubular bolt 101 which is slideable on a bolt guide 117 fixed cantilever fashion to the rear of the marker housing 2 by its head 3. Surrounding the bolt and bolt guide is a mechanism 5 which serves to move the bolt 101 forward when the trigger 7 of the marker is pulled and rearward when the trigger 7 is released. Mechanism 5 comprises a valve 9, preferably a multipath valve, which is operated by a pull on trigger 7 to selectively place in communication a supply of compressed gas for example in a canister 11 attached to the marker 1 with an annular chamber 22 a encircling said bolt 101 and an internal chamber 133 inside said bolt guide 117. Valve 9 can be operated in any way, for example mechanically, electronically, pneumatically or hydraulically.

Bolt 101 is provided with a first external circumferential face 110 with a projected surface area A1 normal to the longitudinal axis of the marker and a second external face 112 with a projected surface area A2 normal to the longitudinal axis of the marker (see enlarged views in FIGS. 3 d and 3 e). Forward driving and rearward driving of the bolt can be controlled by adjusting the pressure of the compressed gas acting on each these faces. Rearward driving being achieved when the product of the surface area A1 and the pressure acting on it is greater than the product of the surface area A2 and the pressure acting on it, and forward driving being achieved when the opposite relationship occurs.

As shown in FIGS. 2 a, 2 b, 3 a, 4 a and 4 b in more detail, bolt 101 comprises a hollow stepped body 103 with a first, forward, bolt end 105 and a second, rearward, bolt end 107 separated by a tubular bolt wall 109 of length BL. Tubular bolt wall 109 comprises:

a first longitudinally-extending section 111, of external diameter BD1 and internal diameter Bd1, which extends from said first bolt end 105 a distance BL1 towards said second end 107; a second longitudinally-extending section 113, of external diameter BD2 and internal diameter Bd2, which extends from said first longitudinally-extending section 111 a distance BL2 towards said second bolt end 107; wherein external diameter BD2 is greater than internal diameter Bd2 which is greater than external diameter BD1.

Bolt guide 117 comprises a stepped body 119 with a first end 121 and a second end 123 separated by a wall 125 of length GL,

Body 119 comprises:

a first longitudinally-extending section 127 with a maximum external diameter GD1 which extends from said first end 21 a distance GL1 towards said second end 123; a second longitudinally-extending section 129 of maximum external diameter GD2 which extends from said first longitudinally-extending section 127 a distance GL2 towards said second end 123; a third longitudinally-extending section 131 of external diameter GD3 which extends from said second longitudinally-extending section 129 a distance GL3 towards said second end 123; and a longitudinally-extending internal gas storage chamber 133 which is sealed at both ends but which can communicate with the exterior of the bolt guide via at least one longitudinally extending port 135 formed in the wall of the second longitudinally-extending section 129; wherein: GD1 is less than GD2 which is less than GD3; and GD2 is less than or equal to Bd2 which is less than GD3—this limits the rearward movement of bolt 101.

Preferably the sum of GL1 plus GL2 is less than or equal to BL in order to prevent the first end 121 of body 119 from projecting though the bolt 101 when the bolt 101 is in the rearmost position.

During use bolt 101 is prevented from exiting the barrel 4 of marker 1 by a cylindrical bolt housing 6 mounted on the inside of the marker housing 2. Bolt housing 6 has a stepped inner profile 8—the distal end 10 of which has an internal circular rib 12 of width Hl1 in the longitudinal direction and an opening of diameter Hd1 which is equal to or greater than BD1 and less than BD2—thus allowing the first longitudinally-extending section 111 of bolt 101 to pass though it but preventing the second longitudinally-extending section 113 of bolt 101 from passing though it. The longitudinal section 13 of bolt housing 6 which extends from the rearward facing face of rib 12 towards proximal end 14 has internal diameters Hd2 which are equal to or greater than BD2. The outer surface 16 of bolt housing 6 is provided with at least two (but in this embodiment three) longitudinally spaced circumferential ribs 18 a, 18 b and 18 c which seal against the inner surface 20 of marker housing 2. A first annular space 22 a is formed between first rib 18 a and second rib 18 b when bolt housing is mounted in marker housing 2. In the event that only two longitudinally spaced circumferential ribs are used then these must be the ribs 18 a, 18 b which form first annular space 22 a. This annular space 22 a is connectable via a port 24 a in marker housing 2 to valve 9 and compressed gas supply 11. At least one through hole 26 a in the wall of bolt housing 6 leads from annular space 22 a to a variable length annular chamber 28 a which is formed between the inner surface of bolt housing and the external surface of diameter BD1 of bolt 101 and which extends longitudinally from face 110 to the side of rib 12 facing face 110. The length of chamber 28 a is at a maximum when bolt 101 is in the rearmost position, as shown in FIGS. 2 a and 4 a and is at a minimum when bolt 101 has been fired and is in the forward position as shown in FIGS. 2 b and 4 b. The difference in length of annular chamber 28 a between these two positions is the stroke S of the bolt.

A second annular space 22 b is formed between second rib 18 b and third rib 18 c when bolt housing is mounted in marker housing 2. This annular space 22 b is connectable via a port 24 b in marker housing 2 to compressed gas supply 11. At least one through hole 26 b in the wall of bolt housing 6 leads from annular space 22 b to the interior of bolt housing 6.

The dimensions of bolt housing 6, bolt guide 117 and bolt 101 are arranged so that the forward longitudinal movement of bolt 101 is stopped when face 110 (or optionally a resilient buffer 151 provided on face 110) comes into contact with rib 12 and the rearward longitudinal movement of bolt 101 is stopped when face 112 comes into non-sealing contact with the first portion of bolt guide 117 which has a diameter greater than Bd2.

When bolt 101 is in the rearward position compressed gas can pass from compressed air supply 11, port 24 b, annular space 22 b, the non-sealing contact between face 112 and the first portion of bolt guide 117 which has a diameter greater than Bd2 and at least one longitudinally extending port 135 to longitudinally-extending internal gas storage chamber 133. Additionally compressed gas can pass from compressed gas supply 11 via valve 9, port 24 a, and through hole 26 b in the wall of bolt housing 6 into annular space 22 a where it exerts a rearward force on face 110 which is greater than the forward force on face 112 thus holding the bolt in the rearward position. Sealing means 161 a such as an O-ring, X-ring, V-ring, resilient washer or equivalent, in a circumferential groove is arranged between the exterior of bolt 101 and the interior of bolt housing 6, and sealing means 161 b such as an O-ring, X-ring, V-ring, resilient washer or equivalent, is arranged between the exterior of bolt guide 117 of diameter GD2 and the interior of bolt 101 of diameter Bd2 and sealing means 161 c such as an O-ring, X-ring, V-ring, resilient washer or equivalent, is arranged between the interior of housing 6 of diameter Hd1 and the exterior of bolt 101 of diameter BD1 so that in this position the compressed gas can exert a forward force on face 112 but cannot escape from the longitudinally-extending internal gas storage chamber 133, and the gas exerting a rearward force on face 110 cannot escape from between the exterior of bolt 101 and the interior of bolt housing 6. The surfaces of faces can have any shape such as flat or sloping.

In this embodiment of the invention when trigger 7 is pulled to fire the marker, valve 9 is actuated so that compressed air is vented from variable length annular chamber 28 a and bolt 101 moves forward as the forward force exerted on face 112 overcomes the force exerted on face 110 which diminishes as the compressed air is vented from annular chamber 28 a. The proximal end of bolt 101 is provided with an internal, longitudinally extending portion of internal diameter Bd2 which seals against sealing means 161 b. The portion of internal diameter Bd2 extends towards the distal end so that when bolt 101 is in the rearward position the portion of bolt of internal diameter Bd2 is sealed by sealing means 161 b against bolt guide 116 but as soon as bolt moves forward then this portion of internal diameter Bd2 starts to move away sealing means 161 b thereby opening a gap between sealing means 161 b and the portion of internal diameter Bd2 which allows compressed gas from internal gas storage chamber 133 via longitudinally extending port 135 to pass the sealing means 161 b and exit into the breech and barrel, thereby propelling the paintball out of the barrel. Bolt 101 travels forward until it is arrested by rib 12. At this position valve 9 is activated to allow compressed gas from supply 111 to enter variable length annular chamber 28 a and push bolt 101 rearwards. At the same time compressed gas refills longitudinally-extending internal gas storage chamber 133 via valve 9, port 24 b, annular space 22 b, longitudinally extending port 135 and after longitudinally extending port 135 is obscured by bolt 101, the non-sealing contact between face 112 and the first portion of bolt guide 117 which has a diameter greater than Bd2. Refilling of compressed gas stops when the pressure in longitudinally-extending internal gas storage chamber 133 is the same as that in supply 11.

FIGS. 3 b, 3 c and 5 a-6 b show further embodiments of bolts in accordance with the present invention. Bolt 101 b shown in FIGS. 3 b, 5 a, 5 b has a third longitudinally-extending section 115 b of external diameter BD3 which extends from said second longitudinally-extending section 113 a distance BL3 towards said second bolt end 5, wherein external diameter BD3 is greater than external diameter BD2. Third longitudinally extending section 115 b is provided with two longitudinally spaced circumferential sealing means, such as O-rings, X-rings, V-rings, resilient washers or equivalents 118 a, 118 b which are intended to seal against the inner surface of bolt housing 6 on either side of port 24 b, thereby preventing compressed gas from exiting through this port.

Bolt 101 c shown in FIGS. 3 c, 6 a and 6 b has a third longitudinally-extending section 115 c of external diameter BD3 which extends from said second longitudinally-extending section 113 a distance BL3 towards said second bolt end 5, wherein external diameter BD3 is greater than external diameter BD2. This forms a face 114 c of area A3 between said second and third longitudinally extending sections 113 respectively 115 c. Third longitudinally extending section 115 c is provided with a single circumferential sealing means, such as an O-ring 118 c which are intended to seal against the inner surface of bolt housing 6 to the rear of port 24 b, thereby allowing compressed gas exiting through this port to exert a rearward force on face 114 c. 

1. Bolt 101 for a gas powered marker 1 wherein said bolt 101 comprises a hollow stepped body 103 with a first bolt end 105 and a second bolt end 107 separated by a tubular bolt wall 109 of length BL characterised in that said tubular bolt wall 109 comprises: a first longitudinally-extending section 111, of external diameter BD1 and internal diameter Bd1, which extends from said first bolt end 105 a distance BL1 towards said second end 107; a second longitudinally-extending section 113, of external diameter BD2 and internal diameter Bd2, which extends from said first longitudinally-extending section 111 a distance BL2 towards said second bolt end 105; wherein external diameter BD2 is greater than internal diameter Bd2 which is greater than external diameter BD1.
 2. Bolt in accordance with claim 1 characterised in that it further comprises, a third longitudinally-extending section 115 b; 115 c of external diameter BD3 which extends from said second longitudinally-extending section 113 a distance BL3 towards said second bolt end 5, wherein external diameter BD3 is greater than external diameter BD2.
 3. Bolt in accordance with claim 1 characterised in that the internal diameter Bd1 of first longitudinally extending section 11 is less than or equal to the internal diameter Bd2 of second longitudinally extending section
 13. 4. Gas powered marker comprising a bolt guide 117 and a bolt in accordance with any of the previous claims slideably mounted on said bolt guide 117, characterised in that said bolt guide 117 comprises a stepped body 119 with a first end 121 and a second end 123 separated by a wall 125 of length GL, wherein said body 119 comprises: a first longitudinally-extending section 127 with a maximum external diameter GD1 which extends from said first end 21 a distance GL1 towards said second end 123; a second longitudinally-extending section 129 of maximum external diameter GD2 which extends from said first longitudinally-extending section 127 a distance GL2 towards said second end 123; a third longitudinally-extending section 131 of external diameter GD3 which extends from said second longitudinally-extending section 129 a distance GL3 towards said second end 123; and a longitudinally-extending internal chamber 133 which is closed at said first end and open at said second end 123; wherein: GD1 is less than GD2 which is less than GD3; and GD2 is less than Bd2 which is less than GD3.
 5. Gas powered marker in accordance with claim 4 wherein the sum of GL1 plus GL2 is less than or equal to BL.
 6. Bolt in accordance with claim 2 characterised in that the internal diameter Bd1 of first longitudinally extending section 11 is less than or equal to the internal diameter Bd2 of second longitudinally extending section
 13. 